Using ssh in a while read loop reading from stdin

Question

I have a shell function that returns a list of hostnames and IP addresses:

$ list_hosts
hostA 10.1.1.1
hostB 10.1.1.2
hostC 10.1.1.3

I want to get a different address for each host:

$ function list_ip6 {
  list_hosts | while read -r hostname ip ; do
    ip6=$(ssh ${ip} ip -o address list eth0 | awk '/scope global/ {print $4;}')
    echo "Host ${name} has IP6 ${ip}"
  done
}

This only prints out the IP6 for the first host returned by list_hosts:

$ list_ip6
Host hostA has IP6 fd57:9e3a:c90e:753f:d625:ccff:feb0:7984/128

The problem appears to be the command substitution on the second line; if I comment that out, it loops over all the hosts:

$ list_ip6
Host hostA has IP6
Host hostB has IP6
Host hostC has IP6

Does the process substitution somehow interfere with reading from the the output of list_hosts?

Is there a good way of doing this in the busybox ash shell? In bash I would just read the lines into an array and loop over the array but of course that's not an option in ash.

Edit to add:

The problem seems to be specifically the ssh connection. If I just print out the local IP6 for each host then it works correctly:

$ function list_ip6 {
  list_hosts | while read -r hostname ip ; do
    ip6=$(ip -o address list eth0 | awk '/scope global/ {print $4;}')
    echo "Host ${name} has IP6 ${ip}"
  done
}
$ list_ip6
Host hostA has IP6 fd57:9e3a:c90e:753f:d625:ccff:feb0:7931/128
Host hostB has IP6 fd57:9e3a:c90e:753f:d625:ccff:feb0:7931/128
Host hostC has IP6 fd57:9e3a:c90e:753f:d625:ccff:feb0:7931/128

The process substitution is okay, it's just that SSH somehow breaks out of the loop.